1. Field of the Invention
The present invention relates to a motor rotor and a method for manufacturing the same.
2. Description of the Related Art
The rotor of an electric motor (for example, a synchronous motor) includes a rotor core constituting a yoke and permanent magnets held on the outer circumferential surface of the rotor core or held inside the rotor core. Known methods for fixing the thus arranged permanent magnets to the rotor core include, for example, a method that uses an adhesive and a method that injects a molten resin by an injection molding machine and then curing the resin.
When the prior known resin injection magnet fixing method is employed, there is concern that a portion of the rotor core may be deformed due to an extremely high injection pressure. A method for suppressing such deformation of the rotor core at the time of resin injection is known, for example, in the following patent documents.
In Japanese Unexamined Patent Publication No. 2007-159245, there is described a method in which a member for suppressing deformation of the rotor core is provided in a recessed portion of an injection molding die and the member is butted against the rotor core to support the strength of the rotor core.
In Japanese Unexamined Patent Publication No. 2002-247784, there is described a method in which, in a magnet embedded rotor, a space is left on the rotor shaft side of a permanent magnet and a resin material is injected into the space thereby alleviating the pressing force exerted on a laminated iron core.